Active phased array antennas are capable of forming one or more antenna beams of electromagnetic energy and electronically steering the beams to targets, with no mechanical moving parts involved. A phased array has many advantages over other types of mechanical antennas, such as dishes, in terms of beam steering agility and speed, having a low profile, low observability (LO) and low maintenance.
A beam-forming network is a major and critical part of a phased array antenna, responsible for collecting all the electromagnetic signals from the array antenna modules and combining them in a phase coherent way for the optimum antenna performance. One major component of the beam forming network is the antenna aperture. In large phased array antennas the antenna aperture is usually comprised of a plurality of smaller subarrays of antenna elements. The use of a plurality of subarrays eases manufacturing constraints on the beam-forming network, allows the antenna to be dynamically reconfigured, and allows for scaleable designs.
In high frequency phased array antennas, however, space constraints often mean that entire rows or columns of antenna elements must be eliminated to accommodate additional subarrays, thus creating gaps between antenna elements. Put differently, the uniform row and column spacing between array elements in a given subarray is disrupted once two or more subarrays are configured to form the antenna aperture, and this disruption is manifested by the gaps between rows and/or columns of antenna elements where two or more subarrays meet. This is especially so for rhombic shaped antenna apertures, where the gaps around the periphery of each subarray, when two or more subarrays are positioned adjacent each other, have made antenna aperture design challenging.
The above-described gaps between rows and/or columns of antenna elements can have a detrimental impact on antenna performance. This may result in antenna pattern degradation and an increased radar cross section for the antenna aperture.